Printer ink is the most expensive liquid, per ml, on the planet. Often when a printer indicates the ink cartridges are empty and should be replaced, the cartridges are in fact still a third full. By refilling separate sets of these supposedly 'empty' cartridges with less expensive liquids - Evian mineral water, Dom Perignon champange and Chanel No.5 perfume - the printer recognises the cartridge is full and continues to print each liquid's respective image.